Siliceous dioxolane derivatives

ABSTRACT

GLYCIDYLOXYPROPYLALKOXYSILANES ARE PRODUCED BY THERMAL TREATMENT OF NOVEL SILICEOUS DIOXOLANE DERIVATIVES OF THE FORMULA:   2-(R=),4-((R&#39;&#39;)A-SI(-OR&#34;)(3-A)-(CH2)3-O-CH2-1,3-DIOXOLANE   WHEREIN A IS 0 OR 1 AND R REPRESENTS AN OXYGEN RADICAL OR TWO HYDROGEN ATOMS AND R&#39;&#39; AND R&#34; EACH REPRESENTS AN ALKYL RADICAL, WHEREIN THE R&#34;&#39;&#39;S CAN BE THE SAME OR DIFFERENT. THE GLYCIDYL PRODUCTS ARE USEFUL AS ADHESIVES.

ABSTRACT OF THE DISCLOSURE Glycidyloxypropylalkoxysilanes are produced by thermal treatment of novel siliceous dioxolane derivatives of the formula:

CH1CHCH1O(CH3) a-EiR. (O R wherein a is 0 or 1 and R represents an oxygen radical or two hydrogen atoms and R and R" each represents an alkyl radical, wherein the R"s can be the same or different. The glycidyl products are useful as adhesives.

BACKGROUND Organosilanes which contain epoxy groups have for some years been attracting a great deal of technical interest. They are used, for example, as adhesives for the combination of certain organic polymers, such as epoxy resins or phenolic resins with glass fibers, fabrics or roving, and for improving adhesion in the bonding of sand molds. Successful attempts have already been made for the improvement of the adhesion between plastics and metals on the basis of the use of such silanes.

The synthesis of these epoxy organosilane esters has hitherto been possible through a variety of methods. For example, organosilane esters containing carbon double bonds are oxidized with peroxides to produce such epoxides. This method, however, is not generally applicable to the synthesisfof the entire class of substances owing to poor compatibility with the sensitive silane esters. On the other hand, it suffers from by-products which necessarily arise from the peroxides and therefore it is economically unprofitable. Furthermore, the use on a large technical scale of the peroxides suitable for this procedure, such as peracetic acid, entails considerable safety risks.

Another known method of manufacturing epoxy organosilane esters is the catalytic addition of hydrogen silane esters onto the carbon double bond of a monoolefinic epoxy compound. The catalysts used for this purpose are essentially simple or complex compounds of nickel, platinum, rhodium or ruthenium.

The disadvantage of this process lies especially in the action of the basic epoxy group on the base-sensitive hydrogen silane esters. This leads on the one hand to competing disproportionation reactions with the formation of higher silane esters and hydrogen silanes. On the other hand, this basicity is so great that it has a poisoning effeet on the catalysts. Since in this process a satisfactory transformation is not achieved until temperatures of 130 C. and up are reached, these competing reactions may become very undesirably evident. In addition, the catalysts also bring about the hydrogenation of the olefinic center of addition. Numerous attempts have therefore been made to overcome these disadvantages by complex variants at the central atoms of the catalysts, and gradual improvements have indeed been achieved, although it has not been possible to completely eliminate the described difliculties.

United States Patent 0 Inasmuch as the catalytic addition of chlorosilanes rather than the sensitive hydrogen silane esters runs into difficulties on account of the basicity of the epoxy compounds, attempts have also been made to use hydrogen fluorosilanes as starting materials. The epoxy organofiuorosilanes thus obtained then have to be reesterified.

This procedure again involves the disadvantage of the introduction of a two-stage process, while the known disadvantages of catalyst poisoning and of the competing hydrogenation reaction are not eliminated. 'In addition, working with hydrogen fluorosilanes requires the expensive safety measures and procedures which are necessarily involved in fluorine chemistry, so that higher first costs are involved in the application of this process.

THE INVENTION It has now surprisingly been found that the above-described ditficulties can be overcome simply by using as the starting products in the synthesis of silane esters containing epoxy groups siliceous dioxolane derivatives which have hitherto been unknown, and subjecting these new compounds to a thermal treatment in which the epoxy group containing silanes form with the yielding of highly volatile substances.

The subject of the invention is new siliceous dioxolane derivatives of the general formula:

in which a=0 or 1 and R represents an oxygen radical or two hydrogen atoms and R and R" represent identical or different alkyl radicals, as well as the use of these derivatives in a process for the manufacture of 3-glycidyloxypropylalkoxysilanes which process is characterized in that the siliceous dioxolane derivatives are subjected to a thermal treatment which results in the yielding of C0 or formaldehyde.

The 3-glycidyloxypropylalkoxysilanes are of the formula:

O I (II) wherein a, R and R" are as defined in reference to (I).

In the above general formulas, R' and R" represent a lower alkyl radical with preferably 1 to 4 carbon atoms e.g. methyl, ethyl, propyl, isopropyl, and n-, s-, tand isobutyl.

The process of the use-of the siliceous dioxolane derivatives may be performed both at normal pressure or in vacuo; e.g. 760 to 1 mm. of Hg. The yielding of CO or formaldehyde takes place at temperatures between about and 240 (3., preferably between about and C.

The cleavage is accelerated, especially when catalysts such as CaO are additionally used.

The splitting ofl? of C0,, or formaldehyde may also be performed by operating in vacuo, it being desirable to operate at the boiling temperature under the corresponding vacuum. Since the glycidyl silane that forms has a lower boiling point than the starting compound, this procedure presents the advantage that the desired end product can be separated immediately from the reaction chamber by interposing a suitable reflux column. The temperature above about 300 C. should preferably be avoided. The temperature should not exceed the decomposition temperature of the substrates. The splitting off of 00 or formaldehyde can also be carried out in the presence of basic metal oxides. This method has the advantage that the temperature, for a given rate of splitting off, can be lower.

Catalytic amounts show a significant effect; stoichiometric" amounts can be used. The alkaline earth oxides or other basic metal oxides, such as zinc oxide, or the alkaline earth carbonates, are given as examples. These compounds are used preferably in quantities catalytic or stoichiomettie to the starting siliceous dioxolane.

The compounds used as the starting substances are previously unknown compounds which are prepared by a method, employing a known type reaction, through the addition of 4- allyloxymethyl-Z-oxo-1,3-dioxolane or 4- allyloxymethyllj -dioxolane onto trialkoxy hydrogen silane or monoalkyl d'ialkoxy hydrogen silane, using platinum compounds as catalysts. The addition takes place at temperatures as low as 70 C., and on account of the masking of the epoxy group, it does not have the abovedescribed disadvantages entailed in the addition of compounds containing double bonds onto hydrogen silanes.

The following are given as examples of suitable starting substances: 4 (3 trimethoxysilylpropoxymethyl)-2- oxo-1,3-dioxolane or 4-(3-trimethoxysilylpropoxymethyl)- 1,3-dioxolane. Both products lead to 3-glyoidyloxypropyltrimethoxysilane, the former with the yielding of carbon dioxide, the latter with the yielding of formaldehyde.

EXAMPLE 1 3-glycidyloxypropyltrimethoxysilane In a vacuum still with a 12-tray column containing a Multifil packing with a void volume of 96%, 840 grams of 4-(3'-trimethoxysilylpropoxymethyl)-2-oxo-1,3-dioxolane are heated with a bottom mass of 170 g. of dry calcium oxide at 5 Torr (mm. Hg) to a vigorous ebullition at which the temperature is 175 C. Within 3 hours, with a reflux ratio of 8, 701 grams of distillate having a boiling point of 124 to 126 C. (5 Torr) is obtained, which consists of virtually pure 3-glycidyloxypropyltrimethoxysilane and has the following characteristics:

In its index of refraction, density and infrared spectrum, the substance is identical with authentic material.

EXAMPLE 2 2-oxo-4'( 3 '-trimethoxysilylpropoxymethyl) -1,3 -dioxolane The following reaction is performed in a 4-liter multiple-neck flask provided with a leaf stirrer, 2 dropper funnels, an internal thermometer and a reflux condenser with nitrogen gas shielding.

0.5 mil of a 1/ 1'00 molar solution of platinum hydrochloric acid in acetone is stirred into 316 g. of 2-oxo-4- allyloxymethyl-l,3-dioxolane and the mixture is heated to 70 C. at atmospheric pressure. The heater is removed and the reaction is performed by adding simultaneously, drop by drop, |1464 grams of trimethoxysilane and 1580 g. of 2-oxo-4-allyloxymethyl-1,3-dioxolane over a period of 3 hours, sustaining a reaction temperature of 70 C. by means of external cooling at atmospheric pressure. The mixture is stirred for one more hour at 70 C. The colorless to pale yellow crude product consists of 2-oxo-4-(3'- distillation delivers a yield of 3344 g. Boiling point: C. -(2 Torr); n 1.4389; D 1.184; the substance dissolves to form a clear solution in water.

Elemental analysis for C1dH2dQqs i (MW='2]80):

' .lfereerit i The infrared spectrum shows a strong carbonyl band at 1799 cm." which is to be associated withthe C=O group on the dioxolane ring. v

The reaction can also be carried out inthepresence of CaO.

EXAMPLE 3 4-(3'-trimethoxysilylpropoxymethyl) -1,3-dioxolahe E Percent I p C H Sl Calculated 45.1 8.27 10.5

Found 45.3 8.4 10.4

What is claimed is: 1. A siliceous dioxolane derivative of the formula:

\fl v wherein a is O or 1 and R represents oxygen and R and 'R" each represents lower alkyl, wherein the R"s can be the same or diflerent. 1

'2. 'Dioxolane according to claim 1 wherein R and R" is each alkyl of 14 carbon atoms. r

3. Dioxolane according to claim 2 wherein a is 0 and each R" is methyl. 1 e

No references cited.

NORMA s. MIIJESTO'N-E, Primar Examiner;

US. 01. xiii. 260-348 so, 340.9 

